4.2. Definitions of Protocol Status

This document lists a "requirement level" or STATUS for each
protocol. The status is one of "required", "recommended",
"elective", "limited use", or "not recommended".

4.2.1. Required Protocol

A system must implement the required protocols.

4.2.2. Recommended Protocol

A system should implement the recommended protocols.

4.2.3. Elective Protocol

A system may or may not implement an elective protocol. The
general notion is that if you are going to do something like this,
you must do exactly this. There may be several elective protocols
in a general area, for example, there are several electronic mail
protocols, and several routing protocols.

4.2.4. Limited Use Protocol

These protocols are for use in limited circumstances. This may be
because of their experimental state, specialized nature, limited
functionality, or historic state.

4.2.5. Not Recommended Protocol

These protocols are not recommended for general use. This may be
because of their limited functionality, specialized nature, or
experimental or historic state.